MT-ND1 and rheumatoid arthritis: To test the hypothesis that mutations in mitochondrial DNA (mtDNA) are associated with RA, we focused on the MT-ND1 gene for mitochondrially encoded NADH dehydrogenase 1 (subunit one of complex I – NADH dehydrogenase) of synoviocyte mitochondria from RA patients, using tissue from osteoarthritis (OA) patients for controls.